1. Field of the Present Invention
The present invention relates to a microelectromechanical system (MEMS), more particularly, relates to a microelectromechanical system (MEMS) to measure angular rate of a carrier. The system of the present invention includes an angular rate sensor unit, microelectronic circuitry, and signal processing to obtain a highly accurate, sensitive, stable angular rate measurement of the carrier under dynamic environments.
2. Description of Related Arts
An angular rate measurement can be obtained by employing a conventional gyro. Many types of approaches based on various sensing principles used to achieve an angular rate sensor have been invented in the past decades, are currently being invented, and will continue to be invented as the market for angular rate sensors continues to expand. For example, conventional spinning mass gyros are based principally on the Law of the Gyroscope. Existing ring laser gyros and Interferometric Fiber-Optic Gyros are dependant on the Sagnac Effects.
Conventional angular rate sensors have been commonly used in a wide variety of applications. However, their cost, size, and power prohibits their use in emerging commercial applications.
xe2x80x9cMEMSxe2x80x9d stands for xe2x80x9cMicroElectroMechanical Systemsxe2x80x9d, or small electrical/mechanical devices. MEMS devices involve creating controllable mechanical and movable structures using IC (Integrated Circuit) technologies. MEMS include the concepts of Microelectronics and Micromachining. Example MEMS devices include inkjet-printer cartridges, accelerometers that deploy car airbags, and miniature robots.
Microelectronics, the development of electronic circuitry on silicon chips, is a very well developed technology. Micromachining utilizes process technology developed by the integrated circuit industry to fabricate tiny sensors and actuators on silicon chips. In addition to shrinking the sensor size by several orders of magnitude, integrated electronics can be added to the same chip, creating an entire system on a chip. This instrument will result in, not only the redesign of conventional military products, but also new commercial applications that could not have existed without small, inexpensive inertial sensors.
Various MEMS angular rate sensor approaches have been developed to meet the need for inexpensive yet reliable angular rate sensors in fields ranging from automotive to consumer electronics. Single input axis MEMS angular rate sensors are based on either translational resonance, such as tuning forks, or structural mode resonance, such as vibrating rings. Moreover, dual input axis MEMS angular rate sensors may be based on angular resonance of a rotating rigid rotor suspended by torsional springs. The inherent symmetry of the circular design allows angular rate measurement about two axes simultaneously.
However, it is still very challenging work to design and manufacture a MEMS angular rate sensor with high accuracy, keen sensitivity, wide dynamic range, and high stability.
A main objective of the present invention is to provide a system to measure angular rate, wherein the angular rate sensor unit, microeleronic circuitry, and signal processing are fabricated into one silicon chip with the combination of surface micromachining layers of polysilicon and Integrated circuitry (IC) technology to obtain highly accurate, sensitive, stable angular rate measurements under dynamic environments.
Compared with existing MEMS angular rate sensors, the MEMS angular rate sensor of the present invention has several unique features that are described as follows:
1. Hinge to minimize number of resonance modes.
2. Mass distribution for resonance mode linearity.
3. Resonance mode locking circuitry.
4. Displacement regulation for scale factor stability.
5. Temperature stabilization for scale factor and bias stability.
6. Low mechanical damping through moderate vacuum.
7. Pickoff circuitry to minimize bias and scale factor shift.
8. The same driver comb used for both excitation and dither pickoff.
9. Closed loop design for scale factor linearity.
Another objective of the present invention is to provide a microelectromechanical system to measure angular rate. The present invention enables the core micro IMU, which has the following unique features:
(1) Attitude Heading Reference System (AHRS) Capable Core Sensor Module.
(2) Miniaturized (Length/Width/Height) and Light Weight.
(3) High Performance and Low Cost.
(4) Low Power Dissipation.
(5) Dramatic Improvement In Reliability (microelectromechanical systemsxe2x80x94MEMS).
Another objective of the present invention is to provide a microelectromechanical system to measure angular rate. The present invention enables the core micro IMU to be incorporated into an integrated micro land navigator, which has the following unique features:
(1) Miniature, light weight, low power, low cost.
(2) AHRS, odometer, integrated GPS chipset and flux valve.
(3) Integration filter for sensor data fusion and zero velocity updating.
(4) Typical applications: automobiles, railway vehicles, miniature land vehicles, robots, unmanned ground vehicles, personal navigators, and military land vehicles.
Another objective of the present invention is to provide a microelectromechanical system to measure angular rate. The present invention enables the core micro IMU to function as aircraft inertial avionics, which has the following unique features:
(1) Rate Gyro
(2) Vertical Gyro
(3) Directional Gyro
(4) AHRS
(5) IMU
(6) Inertial Navigation System
(7) Fully-Coupled GPS/MEMS IMU Integrated System
(8) Fully-Coupled GPS/IMU/Radar Altimeter Integrated System
(9) Universal vehicle navigation and control box.
Another objective of the present invention is to provide a microelectromechanical system to measure angular rate. The present invention enables the core micro IMU to be a Spaceborne MEMS IMU Attitude Determination System and a Spaceborne Fully-Coupled GPS/MEMS IMU Integrated system for orbit determination, attitude control, payload pointing, and formation flight, which has the following unique features:
(1) Shock resistant and vibration tolerant
(2) High anti-jamming
(3) High dynamic performance
(4) Broad operating range of temperatures
(5) High resolution
(6) Compact, low power and light weight unit
(7) Flexible hardware and software architecture
Another objective of the present invention is to provide a microelectromechanical system to measure angular rate. The present invention enables the core micro IMU to be a marine INS with embedded GPS, which has the following unique features:
(1) Micro MEMS IMU AHRS with Embedded GPS
(2) Built-in CDU (Control Display Unit)
(3) Optional DGPS (Differential GPS)
(4) Flexible Hardware and Software System Architecture
(5) Low Cost, Light Weight, High Reliability
Another objective of the present invention is to provide a microelectromechanical system to measure angular rate. The present invention enables the core micro IMU to be used in a micro pointing and stabilization mechanism, which has the following unique features:
(1) Micro MEMS IMU AHRS utilized for platform stabilization.
(2) MEMS IMU integrated with the electrical and mechanical design of the pointing and stabilization mechanism.
(3) Vehicle motion, vibration, and other interference cancelled by a stabilized platform.
(4) Variable pointing angle for tracker implementations.
(5) Micro MEMS IMU utilized for a micro fire control system for sniper rifles.
Typical applications: miniature antenna pointing and tracking control, laser beam pointing for optical communications, telescopic pointing for imaging, airborne laser pointing control for targeting, vehicle control and guidance.
The present invention can be used as a motion measurement device for both commercial and military systems requiring phased array antenna systems for communication on-the-move. Specific applications include pointing control systems for mobile satellite reception for truckers and radiotelephone and direct broadcast satellite reception. The development of a low cost attitude and heading reference system is critical to the wide deployment of these systems in the commercial arena.